Field of the Invention
The present invention relates to a resin particle and a method of producing the resin particle, and a toner to be used in a recording method involving utilizing an electrophotographic method, an electrostatic recording method, and a toner jet type recording method, and a method of producing the toner.
Description of the Related Art
Resin particles have been used in a wide variety of fields including a paint, an ink, and a toner. In each of the fields, the control of the particle diameters and particle size distribution of the resin particles is important, and in particular, resin particles that achieve both a small particle diameter and the sharpness of their particle size distribution have been desired.
Particularly in the toner field out of those fields, an improvement in quality of an image formed of the toner has been required. The improvement in quality of the image formed of the toner requires the suppression of a variation in charging performance between the particles of the toner. To that end, the uniformization of the particle diameters of the toner, i.e., the sharpening of its particle size distribution is effective, and a “dissolution suspension method” has been proposed as an approach to the sharpening. The dissolution suspension method is a production method involving: dispersing a resin solution, which is obtained by dissolving a resin in an organic solvent in advance, in a dispersion medium in the presence of a dispersant to form a droplet of the resin solution; and then removing the organic solvent to provide a resin particle. A polymer dispersant or a solid fine particle can be used as the dispersant in the dissolution suspension method, and examples of the solid fine particle include an inorganic fine particle and a resin fine particle. A general dispersion medium in the dissolution suspension method is, for example, water. In recent years, however, a production method involving using carbon dioxide in a liquid or supercritical state as a dispersion medium has been developed, and has an advantage in that in the production of the toner particles, energy savings can be achieved by the elimination of a washing step and a drying step. However, the carbon dioxide in a liquid or supercritical state has higher solubility in a resin than in water. Accordingly, when the resin fine particle is used as the dispersant, the stability of the resin fine particle against carbon dioxide is required for the resin fine particle to function as the dispersant to suppress the agglomeration of the droplets.
In addition, in recent years, an electrophotographic apparatus has started to be used under various environments for a long time period in association with the diversification of its use environments. In particular, when the electrophotographic apparatus is used under a high-temperature and high-humidity environment for a long time period, there has been occurring a problem in that a wax exudes to the surface of a toner to cause the agglomeration of the toner particles or to cause member contamination in the electrophotographic apparatus. To cope with the problem, a toner having a core-shell structure in which the surface of a resin serving as a core is covered with a shell resin having a Tg higher than that of the core resin has been proposed. When the toner has the structure, the wax hardly exudes to the surface of the toner. Accordingly, the above-mentioned problems, such as the agglomeration of the toner particles and the member contamination, can be suppressed, and hence a high-quality image can be continuously provided.
According to the dissolution suspension method described in the foregoing, the resin fine particle used as the dispersant adheres to the surface of the droplet of the resin solution, and remains on the surface of the resin particle even after the removal of the organic solvent. Accordingly, a toner having a core-shell structure in which a shell based on the resin fine particle has been formed can be obtained.
In Japanese Patent Application Laid-Open No. 2010-132851, there is proposed a resin particle having a core-shell structure in which a shell based on a resin fine particle that hardly swells in carbon dioxide has been formed, the resin particle being obtained by a dissolution suspension method involving using carbon dioxide as a dispersion medium and using the resin fine particle as a dispersant for the purpose of suppressing the agglomeration of droplets. In the literature, a fine particle based on a crystalline polyester resin, a polybehenyl acrylate or a copolymer resin thereof, or a crosslinkable vinyl resin has been used as the resin fine particle.
In addition, in Japanese Patent Application Laid-Open No. 2013-137535, there is proposed a toner using a resin fine particle containing a resin having a graft type structure using, as constituent components, a moiety having an organic polysiloxane structure and a moiety having an aliphatic polyester structure. In the literature, a toner having a satisfactory particle size distribution is obtained because the toner is produced through the use of the resin fine particle having affinities for both carbon dioxide and a resin solution by a dissolution suspension method involving using carbon dioxide as a dispersion medium. Further, it has been found that the resultant toner satisfies adhesiveness between the resin fine particles, and adhesiveness between the resin fine particle and a core particle, and does not cause any problem resulting from the exudation of a wax.